Method of treating electron-emission elements



Dec. 10, 1929."

s. RUBEN METHOD OF TREATING ELECTRON EMISSION ELEMENTS Filed Jan. 12,1927 wjvwewtoz amue1 Ruben 33 his 61111 1 7;;.C

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Patented Dec. 10, 1929 UNITED STATES PATENT OFFICE SAMUEL RUBEN, OF NEWYORK, N. Y., ASSIGNOR TO RUBEN TUBE CQMPANY, A GOR- PORA.TION OFDELAWARE METHOD OF TREATING ELECTRON-EMISSION ELEMENTS Application medJanuary 12, 1927. Serial No. 160,758

I This invention relates to a method of treating electron emissionelements, and more par-.

ticularlydt relates to a method of treating cathode elements by coatingthem with a dense 5 layer of alkaline earth oxides to increase theelectron'emission beyond that of the metal bases used as cathodes inelectronemission devices.

In the prior art the metal cathodes have had their emissioncharacteristics increased by coatings of alkaline earth oxides by (l)applying to the cathode base an oxide mix ture, or a single oxide, witha binder material, which latter is then carbonized or vaporq ized old,(2) applying an oxide with another compound and decomposing the latterto allow to remain an adherent residue of the de sired oxide and, insome instances, a portion 7 of the binder element in the form of afinely divided metal and (3) passing the cathode base through a moltenmixture of oxides. While such treatment temporarily improves the cathodeemission, for adequate service these coatings lack uniform distribution,proper density and permanent electrical contact with the base, causingexcessive resist-ancelosses in the coating material. At higher voltagesa strong electrostatic attraction away from the cathode to the anodecarries the coating particles with it.

l have found that by applying a coating of alkaline earth oxide materialof high emissivity, such as strontium or barium, to the surface of thecathode element and, after drying the coating and driving off the binderelement, heating the coating material to a point just below its meltingtemperature and compressing it, there remains an oxide coating that isdense, uniformly distributed and of low electrical resistance, andhaving a life and efliciency greatly above that obtained.

5 under compression and on to a reel. As

the wire passes over heated dryer 3, the binder element is driven oilandthe oxide coated wire is carried to compression rolls with the oxidecoating at approximately the melting temperature of the oxides, therollers compressing the coating mass and making it more dense andadherent to the metal base, and therefore giving the cathode element ahigher degree of emissivity and longer life.

What I claim is:

1. The method of treating an electron emission element which consists inapplying a mixture of an alkaline earth oxide and a binder material tothe surface of the element, heating the coating layer on the element andcompressing the coating layer at a temperature close to its meltingtemperature.

2. The method of treating an electron emission element which consists inapplying a mixture of alkaline earth oxides and a binder material to thesurface of the element, heating the applied mixture on the element andcompressing the coatingof the element at a temperature below the meltingtemperature of the coating mixture of oxides.

3. The method of treating an electron emission element which consists inapplying to the surface of the element a mixture of stron tium andbarium oxides with a binder material, heating the coated element andcompressing the applied coating of oxides while heated to a plasticcondition.

4. The method of treating an electron emission element which consists inimmersing the element in a mixture of strontium and barium oxides p witha binder material, withdrawing the element and drying the coating ofoxides adhering to the element, heating the coating to a temperaturejust below its melt- 5. The method of treating an electron emissionelement which consists in applying a mixture of an alkaline earth oxideto the surface of the element, heating the coating layer on 5 theelement and compressing the coating layer at a temperature close to itsmelting temperature.

In testimony whereof, SAMUEL RUBEN has signed his name to thisspecification this tenth 1 day of January, 1927.

Y SAMUEL RUBEN.

